Plastic container and blank



Nov. 29, 1966 c. E. PALMER ETAL PLASTIC CONTAINER AND BLANK OriginalFiled July 18, 1962 5 Sheets-Sheet 1 INVENTORS' CHARLES E. PALME R JOSEPH 5. LE MANSKI ATTORNEY Nov. 29, 1966 c. E. PALMER ETAL PLASTICCONTAINER AND BLANK Original Filed July 18, 1962 5 Sheets-Sheet 2 Nov.29, 1966 c. E. PALMER ETAL PLASTIC CONTAINER AND BLANK Original FiledJuly 18, 1962 5 Sheets-Sheet 3 FIG. I2

FIG. I3

INVENTORS CHARLES E. PALMER JOSEPH S. LEMANSKI /Zz;,c%4@

ATTORNEY United States Patent 3,233,349 PLASTIC CONTAINER AND BLANKCharles E. Palmer, Somers, Conn., and Joseph S. Lemar:-

ski, East Longrneadow, Mass, assignors, by mesne assignments, toMonsanto Company, St. Louis, Mo, a corporation of Delaware Originalapplication July 18, 1962, Ser. No. 210,639. Divided and thisapplication June 6, 1963, Ser. No.

21 Claims. (Cl. 229-39) This application is a division of our copendingapplication, Serial No. 210,639, filed July 18, 1962, and now abandoned.

The present invention relates to containers, and more particularly tocontainers cold-folded from plastic sheet material and to the blankstherefor and the method of folding the blanks into the containers.

In United States Patent No. 2,954,725, granted to Charles E. Palmer,there is disclosed a novel method and apparatus for cold-foldingsynthetic plastic sheet material having the characteristics ofsemi-rigidity and ability to take and retain a fold such as biaxiallyoriented polystyrene. In cold-folding such plastic sheet material, it isgenerally necessary to fold the plastic sheet material beyond 90 degreesin order to obtain the desired permanent set of the fold, and it is alsonecessary to employ locks which will resist high stresses over arelatively wide linear distance to avoid concentration of stress at anyone linear point such as would produce tearing of the plastic sheetmaterial. It is desirable to design the carton and locks so thatstresses will not produce delamination or crazing in highly orientedmaterial so as to avoid discoloration and marring of the surface.

It is an object of the present invention to provide a novel six-sidedcontainer fabricated from synthetic plastic sheet material which ishighly attractive and relatively rigid in assembly to provide arelatively high-strength package protecting the goods received therein.

Another object is to provide a novel blank of synthetic plastic sheetmaterial and a method of cold-folding the blank into such ahigh-strength container at relatively high speeds.

It is also an object to provide a novel interlock for overlying panelsof plastic sheet material which is of high strength and will limitrelative displacement of the panels in any direction.

A further object is to provide a mechanical lock for overlying panelswhich is simply made and which is of such construction thatdisengagement is quite difi'icult to effect and which may be used as ameans of detecting pilferage or tampering.

A still further object is to provide a blank and highspeed foldingmethod wherein the blank may be folded into condition to receive theintended contents in one complete revolution of a folding mandrel withthe necessary locks and engagements being made during the rotation ofthe mandrel.

Other objects and advantages will be readily apparent from the followingdetailed specification and the attached drawings wherein;

FIGURE 1 is a perspective view of a container embodying the presentinvention;

FIGURE 2 is a fragmentary perspective view of the bottom end of thecontainer of FIGURE 1;

FIGURE 3 is a fragmentary perspective view to an enlarged scale of alock on the body portion;

FIGURE 4 is a fragmentary perspective view to an enlarged scale of aslip lock on the bottom end of the container;

FIGURE 5 is a sectional view along the line 5-5 of FIGURE 4;

Patented Nov. 29, IEEE ice FIGURE 6 is a plan view to a reduced scale ofthe blank for the container of FIGURE 1;

FIGURE 7 is a similar view of the blank of FIGURE 6 with the lines ofintended fold indicated in dotted line;

FIGURE 8 is a perspective view showing diagrammatically the first stepin folding the blank of FIGURE 6 into the container of FIGURE 1;

FIGURE 9 is a fragmentary end view showing the blank positioned forfurther folding by a folding mandrel;

FIGURE 10 is a perspective view showing diagrammatically the next stepin the folding sequence;

FIGURE 11 is a similar view showing another step in the foldingsequence;

FIGURE 12 is a similar view showing a further step in the foldingsequence;

FIGURE 13 is a similar view showing the last fold being made in the bodyportion;

FIGURE 14 through 16 are sectional views showing diagrammatically theengagement of the interlock of the present invention; and

FIGURE 17 is a fragmentary perspective view diagrammaticallyillustrating the folding of the top end flaps.

We have now found that the foregoing and related objects can be attainedby a container integrally formed from a blank of synthetic plastic sheetmaterial and having front, rear and side wall panels forming arectangular body and a locking flap on a side panel which overlies therear panel and has a locking tab thereon engaged in a locking incisionin the rear panel. Along the bottom edge of the wall panels are provideda bottom end wall flap, a pair of dust flaps, and a locking fiap whichextend perpendicularly thereto and are engaged to provide the bottomclosure. The locking flap is located upon the edge of the one side wallpanel and has a locking tab which engages in an incision in the end wallfiap which is located upon the other side wall panel. Along the top edgeof the wall panels are provided a pair of dust flaps and an elongatedflap which is folded to provide an end flap overlying the dust flaps anda tuck or locking flap extending perpendicularly thereto along thesurface of the body of the container to provide a releasable closure forthe container although a similar locking tab and incised end wall flapmay be employed for a strong lock in place of the simple tuck flap is sodesired.

In the method of folding the blank of the present invention into thecontainer, a single mandrel is employed for forming the elongated foldsdefining the var-ions wall panels of the body with a preliminary stepbeing the formation of a transverse fold across the bottom end of theblank to fold and set up the bottom wall flaps. The blank with the endfold is then supported upon a series of pivotally mounted supportmembers having their axes coinciding with the intended lines of fold anda top surface or pad of resiliently deformable material. The mandrel hasits side faces dimensioned to correspond with the intended width of thewall panels and to align the edges with the intended lines of fold. Thesides of the mandrel adjacent the edges are undercut to provide knifeedges along the sides. The mandrel is supported for rolling movementlaterally over the several support members so as to depress the plasticmaterial of the blank into the resiliently deformable material of thepads, which deformation also forces the plastic material about theundercut side edges of the mandrel to effect the desired fold therein.As the mandrel rolls along the blank from pad member to pad member, thedust flaps and locking flaps are engaged with the bottom end wall flap;and, as the mandrel makes the final fold for the locking flap along theside of the front panel, the locking tab thereon is engaged in theincision of the adjacent side wall panel.

Thus, the blank is ready and speedily folded into the container formready to receive the contents. The folds in the top end fiaps areconveniently effected by a simple folding blade which is inserted intoposition with its edges aligned with the intended folds in the dustflaps and top flap, and die pads of resiliently deformable material aremoved against the blank and folding blade so as to cause the resilientlydeformable material to flow about the blank and folding blade and forcethe plastic material about the edges of the blade and form the foldtherein. The fold defining the tuck fiap can be made either before orafter making the other folds either by moving a folding blade towards asupporting pad of resiliently deformable material or vice versa.

The lock of the present invention is formed by provid ing a complexcurvilinear incision in the underlying panel which includes a pair ofopposed and aligned generally S-shaped slits having opposed arcuateportions pointing towards each other at the ends of the slits spacedaway from the inner or free end of the overlain portion of the panel andreversely curved arcuate portions with terminal portions extendingtowards each other at the end thereof adjacent the inner or free end ofthe panel. A transverse slit pointing towards the inner or free end ofthe panel intersects the S-shaped slits at the opposed arcuate portionsat a point spaced from the point of their closest proximity towards theinner or free end of the panel and provides a pair of hinged flapsbetween the S-shaped slits. The overlying locking flap is provided onits outer edge with a projecting locking tab of generally dovetailedconfiguration having a free end of greater width than the root portionthereof and of greater width than the spacing between the S-shaped slitsat the point of closest proximity between the opposed arcuate portionsand at the point of greatest separation between the reversely curvedportions. The width of the tab tapers to a reduced dimension at the rootwhereat it is of lesser dimension than the spacing between the reverselycurved portions of the S-shaped slits at their point of greatestseparation. In this manner, the locking tab may be thrust through theincision and engaged behind the underlying panel with the hinged flapdefined by the opposed arcuate portions of the S-shaped slits and thetransverse slit resiliently bearing against its top or outer surface ofthe tab and the hinged flap defined by the reversely curved portions andtransverse slit resiliently bearing against its inner or bottom surface.The tapered side edges of the tab butt against the arcuate sides of theopposed S-shaped slits to limit movement transversely and are retainedfrom movement in the major direction of the slits by the width of thefree end of the tab which is greater than the width between the slits attheir point of closest proximity and also greater than the width betweenthe reversely curved portions.

Turning now in detail to the attached drawings, FIG- URE 6 illustrates ablank embodying the present invention generally designated by thenumeral 1 which is folded into the container of FIGURES 1 through 5. Theblank 1 is integrally formed of synthetic plastic sheeting which willtake and hold a fold and which is relatively rigid while providingresiliency to resist the normal stresses and impacts to which thecontainer may be subjected during usage. The blank is incised along itsedges at the lines of intended fold to define top and bottom end panels,but the surfaces of the blank are smooth and unscored or otherwiseunbroken.

More particularly, as best seen in FIGURE 7 wherein the dotted linesindicate the intended lines of fold, the body portion of the blankprovides sequentially a rear wall panel 2 having a pair of spacedincisions 4 therein adjacent the free end thereof, side wall panel 6,front wall panel 8, side wall panel 10 and the locking flap 12 with itspair of locking tabs 14 on its outer edge which engage in the incisions4 of the rear wall panel 2. The cuts in the blank provide a pair of dustflaps 16 along the bottom edge of the rear and front wall panels 2, 8, alocking flap 28 on the side wall panel 10, and a bottom end wall flap 18upon the side panel 6. The bottom end wall flap 18 has a pair of arcuateincisions 20 adjacent the inner end thereof in which engage theprojecting noses 22 on the sides of the dust flaps 16 which overlie thebottom end wall flap 18. As best seeen in FIGURES 4 and 6, the sides ofthe dust flaps 16 taper inwardly towards the noses 22 to facilitatepassage of the noses 22 into the arcuate incisions 20 during folding asshown in FIGURE 4 and as will be pointed out more in detail hereinafter.Adjacent its free end, the bottom end wall flap 18 is provided with alocking incision 24 in which engages the locking tab 26 of the lockingflap 28. Thus, as shown in FIG- URE 2, the bottom end wall flap 18 andthe dust flaps 16 interengage and are locked in position by theoverlying locking flap 28 to provide a substantially rigid andhighstrength closure for the bottom end of the container.

At the opposite or top edge of the body portion in the erected position,cuts in the blank provide dust flaps 30 on the side wall panels 6, 10and an elongated flap generally designated by the numeral 32 on the rearwall panel 2. The flap 32 is folded as indicated by the dotted line inFIGURE 7 to provide a top end wall panel portion 34 overlying the dustflaps 30 and a tuck flap portion 36 extending normally thereto along theinner surface of the front wall panel 8, thus enabling facile openingand closing of the container. Due to the inherent resiliency of theplastic sheet, the tuck flap portion 36 is biased against the surface ofthe front wall panel 8, thus enabling facile opening and closing of thecontainer. Due to the inherent resiliency of the plastic sheet, the tuckflap portion 36 is biased against the surface of the front wall panel 8to provide a relatively secure closure.

Turning now in detail to the interlock of the present invention which isbest shown in FIGURE 3 with respect to the lock for the side wall panelsand FIGURES 14 through 16 with respect to the lock for the bottom endwall panel, the underlying panel is provided with a complex curvilinearincision including an S-shaped slit 38 and an inverted S-shaped slit 40spaced therefrom disposed so that the slits have opposed arcuateportions pointing towards each other at the ends spaced away from thefree end of the panel and reversely curved portions with terminalportions extending towards each other at the ends adjacent the free endof the panel. A transverse arcuate slit 42 pointing towards the free endof the panel intersects the S-shaped slits 38, 40 at the opposed arcuateportions but spaced towards the free end of the panel from their pointof closest proximity. In this manner, a pair of hinged flaps 44, 46 areprovided between the S-shaped slits 38, 40.

The overlying panel or flap (numeral 12 in FIGURE 3; numeral 28 inFIGURES 14-16) has a locking tab (numeral 44 in FIGURE 3; numeral 26 inFIGURES 14- 16) extending therefrom which is generally of dovetailedconfiguration with its free end being of greater width than its rootportion and also of greater width than the spacing between the S-shapedslits 33, 40 at the point of closest proximity between the opposedarcuate portions and the point of greatest separation between thereversely curved portions. The sides of the locking tab taper inwardlyto the root portion which is of greater :width than the spacing betweenthe opposed arcuate portions of the slits at their point of closestproximity but of lesser width than the spacing between the reverselycurved arcuate portions adjacent the free end of the panel at theirpoint of greatest separation.

Because of the inherent resiliency of the synthetic plastic sheetmaterial, the locking tab can be bent and thrust through the slits 38,40 adjacent the free end of the panel so that it overlies the flap 44which resiliently bears against its inner surface and it in turn isoverlain by the flap 46 which resiliently bears upon its outer surface.Since the locking tab, including its root portion, is of greater widththan the spacing between the opposed arcuate portions of the slits 38,40 at their point of closest proximity, movement of the tab in thedirection away from the free end of the underlying panel is limited bythe abutment of its side edges against the edges of the opposed arcuateportions of the slits which decrease in distance of separation to theirpoint of closest proximity. Movement of the tab towards the free end ofthe panel is limited by the bottoming of the tab in the reversely curvedarcuate portions since the free end of the tab is of greater width thanthe distance between the reversely curved portions at their point ofgreatest separation. By proper dimensioning of the tab and incision, thetab 14 can be seated within the incision so that the side edges of itsroot portion are in close proximity to the reversely curved arcuateportions adjacent the free end of the panel to minimize even further thelittle lateral movement which is permitted before the side edges of thetab abut against the sides of the slits. Since the overlying panels areclamped together by the inherent resiliency of the flaps 44, 46, thereis sub stantially no tendency for external bowing and thus substantiallyparallel external surfaces are provided.

The method of folding the blank into the container is diagrammaticallyillustrated in FIGURES 8 through 17. The first step is illustrated inFIGURE 8 wherein the blank I is supported upon a die pad 48 ofresiliently deformable material, such as rubber, along the intersectionof the bottom flaps with the body panels. A rigid folding blade 50presses the blank into the rubber-like material of the die pad 48 andcauses the rubber-like material to flow and press the blank about theedge of the folding blade 50. As pointed out in the aforementionedPalmer United States Patent No. 2,954,725, the blade 59 is preferably atan acute angle with respect to the surface of the blank 1 so that theflaps will be folded about the edge of the blade to an angle greaterthan 90 degrees, thus overfolding the plastic material to compensate forany inherent relax characteristics therein and provide a permanent bendor fold therein.

As seen in FIGURES 9 and 10, the blank 1 is then supported upon a seriesof pivotally mounted rocker support members 54, 56, 58 and 6t and theblank 1 is located thereon with the intended lines of fold in the bodyportion in substantial alignment with the axes of pivotal movement. Anend support 62 and intermediate supports 64 between the several supportmembers are preferably provided. The several rocker supports 54-6L theend support 62 and the intermediate supports 64 are each provided with apad 66 of resiliently deformable or rubberlike material upon which theblank 1 is disposed.

A folding mandrel 68 is carried by the support arm 70 which extendstherefrom beyond the upper end flaps for rolling movement laterally overthe blank and supports. The mandrel 63 is or generally rectangularconfiguration with its sides dimensioned so that the side edges willalign with the intended lines of fold in the body of the blank and theaxes of the rocker support members during rotation of the mandrel. Asbest seen in FIGURE 9, the sides of the mandrel 68 are provided withundercut portions 72 adjacent the edges to provide knife-like edges '74.

As best seen in FIGURE 9, the rocker supports 54, 56, 58 and 60 arepreferably biased in the at-rest position to a position wherein theupper surface is slightly inclined towards the folding mandrel 68 toensure firm engagement with the mandrel 68 as it rolls thereonto and tolimit or prevent slippage of the blank therebetween. An angle of about 8to 18 degrees has proven satisfactory. By the pivotal mounting of therocker supports, the supports roll with the rotating mandrel to maintainthe blank in contact with the surface thereof. This pivotal support hasbeen found to accommodate variations in the relative speed of rotationand speed of lateral movement of the mandrel.

In FIGURE 10, the mandrel 68 has rolled and pressed the plastic sheetmaterial of the blank 1 into the pad 66 of deformable material on therocker support member 54 and the resiliently deformable material thenflows to press the plastic sheet material about the knife edge 74 intothe undercut recesses 72 to overfold the plastic sheet material andprovide a permanent fold. As the mandrel 68 is making the fold, theresilient material of the pad 66 holds the rear panel 2 against the sideof the mandrel 68, and a finger 76 press-es against the dust flap 16 andthereby the bottom end wall flap 18 to guide the nose portion 22 of thedust fiap 16 into the arcuate incision 20. As the mandrel 68 continuesto roll, the rocker support member 54 pivots in the direction of itsrotation to prevent slippage of the blank relative to the mandrel.

In FIGURE 11, the second told is being made on the rocker support 56 anda finger '78 simultaneously presses against the other dust flap 16 toguide the nose 22. into the arcuate incision 261i. In FIGURE 12, thethird fold is being made upon the rocker support member 58. As themandrel 68 continues to roll and the side wall panel portion of theblank rests against the bottom of the mandrel 68, the intermediatesupport 64 between the rocker support members 58, 60, a finger 82press-es against the locking tab 26 to thrust it inwardly of the lockingincision 24 as shown in FIGURES 14 through 16.

As the mandrel 68 rolls over the last rocker support member 60, the lastfold of the body defining the locking flap 12 is made and, as themandrel 68 continues to roll, the locking flap 12 moves into positionclosely overlying the rear panel 2 and the fingers thrust the lockingtabs 14 inwardly of the incisions 4 to lock the body panels in assemblyand provide a container body ready to receive the merchandise to beplaced therein.

As shown in FIGURE 17, after the container has been filled, a foldingblade 84 carried by the support arm 86 is inserted over the top edge ofthe front panel 8 into the top of the container with its edges alignedwith the lines of intended fold in the dust flaps 30 and elongated flap32.

As shown, the upper edge of the front panel 8 is spaced below theintended lines of gold and the cuts defining the several flaps so as tocompensate for the thickness of the folding blade 84 which extendsthereover. Die supports 88 are carried by support arms 92 and spacedabout the side panel 10, the rear panel 2, and side panel 6 for movementrelative thereto and have pads 90 of resiliently deformable material ontheir faces adjacent the container. When the supports 88 are pressedagainst the container, the rubber-like material flows and forms theplastic sheet material about the edges of the folding blade 84 to makethe folds therein defining the top flaps.

Either before or after making the above folds, the fold defining thetuck flap 36 can be similarly made by use of a separate folding bladeand die pad of resilient material (not shown).

As can be seen, the folding operations are readily adapted to automaticpackaging machinery and can be conducted at rapid speeds on theproduction lines. In place of the simple tuck flap closure for the upperend wall, a mechanical interlock can also be utilized.

The synthetic plastic sheet material should be semirigid with sufficientflexibility to accommodate stresses and impacts occurring during normalurge. The material should also have the characteristics of beingfoldable and retaining a fold in accordance with the aforementionedPalmer patent. From the standpoint of optimum aesthetic qualities andvisibility, the plastic sheeting should be clear and relativelyresistant to scratching during normal usage. Although a number ofplastic materials may be satisfactorily employed, biaxially orientedpolystyrene of about 5 to 15 mils thickness has been advantageouslyemployed because of its clarity, high strength and semi-rigidity coupledwith sufficient resiliency and flexibility to provide durable folds andresistance to normal impacts.

As can be readily appreciated, the container of the present invention ishighly attractive and relatively rigid in assembly to provide ahigh-strength package. The

mechanical interlock of the present invention is of high strength andlimits relative displacement of overlying panels even to the point ofcausing damage to the panels to effect disengagement. The blank andmethod enable the erection of the container speedily and in simplesequences adapted to automatic equipment in high-speed production lines.

Having thus described the invention, we claim:

1. An unscored container blank integrally formed of semi-rigid syntheticplastic sheet material and including a body portion adapted to becold-folded into four wall panels defining a container body ofrectangular configuration and a side-locking flap along one outer sidethereof, said blank having a locking tab on said one outer side and acooperating locking incision adjacent the other outer side thereof forinterengagement upon folding of the blank into the rectangular bodyconfiguration, said blank being incised along one edge at the lines ofintended fold for the wall panels of the body to provide a bottom endwall flap, a pair of dust flaps and an endlocking flap and adapted toprovide a closure for one end of the container, said end-locking flapand end-wall flap being spaced apart by a dust fiap and one of saidlocking fiap and end-wall flap extending from the portion of the blankadjacent said locking flap of the body portion, one of said locking flapand end Wall flap having a locking incision therein and the other ofsaid locking flap and end wall flap having a locking tab thereonengageable in said incision to provide a firm closure, said blank beingincised along the other edge thereof at the lines of intended fold forthe said wall panels to provide flaps adapted to be folded into aclosure for the other end of said body, at least one of said lockingincisions being comprised of a pair of spaced curvilinear slits and aslit extending transversely thereof and intersecting said curvilinearslits intermediate their length to provide a pair of hinged flaps, thespacing between said curvilinear slits varying along the length thereof,the cooperating locking tab being of generally dovetailed configurationwith its free end being of greater width than the spacing between saidcurvilinear slits at their point of widest divergence and with its sidestapering to a root portion of lesser width than the spacing between thecurvilinear slits at their point of greatest divergence, said one tabbeing adapted to extend inwardly of said one locking incision wherebysaid tab will overlie the hinged flap adjacent the edge of theunderlying panel and the other of the hinged flaps defined by saidincision will overlie said tab and said hinged flaps will resilientlybear against the surfaces of said one tab to provide firm engagement.

2. The blank in accordance with claim 1 wherein said locking tab is onthe locking flap and the incision is on said end wall flap.

3. The blank in accordance with claim 1 wherein said synthetic plasticsheet material is biaxially oriented polystyrene of 5 to mils thickness.

4. The blank in accordance with claim 1 wherein each of said lockingincisions is comprised of a pair of opposed generally S-shaped slits anda slit extending transverely thereof and intersecting said S-shapedslits, said S-shaped slits having opposed arcuate portions at the endsspaced away from the edge of the blank and reversely curved portionswith their termini extending towards each other at the ends adjacent theedge of the blank, said transverse slit intersecting said opposedarcuate portions at a point spaced towards the edge of the blank fromtheir point of closest proximity and providing a pair of hinged flapsbetween said S-shaped slits and wherein each of said locking tabs is ofgenerally dovetailed configuration with its free end being of greaterwidth than the spacing between said S-shaped slits, said tabs taperinginwardly to a reduced width at the root portion which is of greaterwidth than the spacing between the opposed arcuate portions at theirpoint of closest proximity but of lesser width than the spacing betweenthe reversely curved arcuate portions at their point of greatestseparation, said tabs being adapted to extend inwardly of said incisionsat a point spaced towards the edge of the underlying panel from thepoint of closest proximity between said opposed arcuate portions withthe sides of its free end portions being disposed along the innersurface of the underlying panels outwardly of said incisions at saidopposed arcuate portions whereby said tabs will overlie the hinged flapsadjacent the edges of the underlying panels and the others of saidhinged flaps will overlie said tabs and said hinged flaps willresiliently bear against the surfaces of said tabs to provide firmengagement.

5. An unscored container blank integrally formed of semi-rigid syntheticplastic sheet material and including a body portion adapted to becold-folded into four wall panels defining a container body ofrectangular configuration and a side locking flap along one outer sidethereof adapted to overlie the wall panel provided by the other outerside thereof, said blank having a locking tab on said one outer sidethereof and a cooperating locking incision adjacent the other outer sidethereof for interengagement upon folding of the blank into therectangular body configuration with the locking flap overlying the wallpanel provided by the other outer side of the blank, said blank beingincised along one edge at the lines of intended fold for the wall panelsof the body to provide an end locking flap on the Wall panel portionadjacent the body locking flap, a pair of dust flaps on the wall panelportion adjacent to said wall panel portion having the end wall flap andon the wall panel portion at said other outer side of the blank, and anend wall fiap on the wall panel portion between those having the dustflaps, said end wall flap having a locking incision therein and said endlocking flap having a locking tab thereon engageable in said incision toprovide a firm closure for one end of the container, said blank beingincised along the other edge thereof at lines of intended fold for thesaid wall panels to provide flaps adapted to be folded into a closurefor the other end of said body, at least one of said locking incisionsbeing comprised of a pair of spaced curvilinear slits and a slitextending transversely thereof and intersecting said curvilinear slitsintermediate their length to provide a pair of hinged flaps, the spacingbetween said curvilinear slits varying along the length thereof, thecooperating locking tab being of generally dovetailed configuration withits free end being of greater Width than the spacing between saidcurvilinear slits at their point of widest divergence and with its sidestapering to a root portion of lesser width than the spacing between thecurvilinear slits at their point of greatest divergence, said one tabbeing adapted to extend inwardly of said one locking incision wherebysaid tab will overlie the hinged flap adjacent the edge of theunderlying panel and the other of the hinged flaps defined by saidincision will overlie said tab and said hinged fiaps will resilientlybear against the surfaces of said one tab to provide firm engagement.

6. The blank in accordance with claim 5 wherein said blank has a pair oflocking tabs spaced apart on the one outer side thereof and a pair oflocking incisions spaced apart adjacent the other outer side thereof.

7. An unscored container blank integrally formed of semi-rigid syntheticplastic sheet material and including a body portion adapted to becold-folded into four wall panels defining a container body ofrectangular configuration and a body-locking flap along one outer sidethereof adapted to overlie the wall panel provided by the other outerside thereof, said blank having a pair of spaced locking tabs on saidone outer side thereof and a pair of cooperating locking incisionsadjacent the other outer side thereof for interengagement upon foldingof the blank into the rectangular body configuration with thebody-locking flap overlying the wall panel provided by the other outerside of the blank, said blank being incised along one edge at the linesof intended fold for g the wall panels of the body to provide an endwall flap, a pair of dust flaps and an end-locking flap extending fromone edge of the wall panel portions and adapted to be folded to extendnormally to said wall panel portions and interengage to provide aclosure for one end of the container, said end-locking flap and end wallfiap being spaced apart by a dust flap and said locking flap extendingfrom the wall panel portion of the blank adjacent said body-lockingflap, said end wall flap having a locking incision therein adjacent thefree end thereof and said locking flap having a locking tab thereonengageable in said locking incision to provide a firm closure for oneend of the contaner, said blank being incised along the other edgethereof at lines of intended fold for the said wall panels to providefiaps adapted to be folded into a closure for the other end of thecontainer, said locking incisions being each comprised of a pair ofopposed generally S shaped slits and a slit extending transverselythereof and intersecting said S-shaped slits, said S-shaped slits havingopposed arcuate portions at the ends spaced away from the edge of theblank and reversely curved portions with their termini extending towardseach other at the ends adjacent the edge of the blank, said transverseslit intersecting said opposed arcuate portions at a point spacedtowards the edge of the blank from their point of closest proximity andproviding a pair of hinged flaps between said S-shaped slits, saidlocking tabs each being of generally dove-tailed configuration with itsfree end being of greater width than the spacing between said S-shapedslits and tapering inwardly to a reduced width at its root portion whichis greater in width than the spacing between the opposed arcuateportions at their point of closest proximity but of lesser width thanthe spacing between the reversely curved arcuate portions at their pointof greatest separation, said tabs being adapted to extend inwardly ofsaid incision at a point spaced towards the edge of the underlying panelfrom the point of closest proximity between said opposed arcuateportions with the sides of its free end portion being disposed along theinner surface of the underlying panel outwardly of said incision at saidopposed arcuate portions whereby said tabs will overlie the hinged flapadjacent the outer edge of the underlying panel and the other of saidhinged flaps will overlie said tab and said hinged flaps willresiliently bear against the surfaces of said tab to provide firmengagement.

8. The blank in accordance with claim 7 wherein said blank is incisedalong the said other edge to provide a pair of dust fiaps and anelongated fiap therebetween, said dust flaps extending from the otheredge of the wall panel portions having said end locking flap and endwall fiap and said elongated flap being dimensioned to be folded toprovide an end wall portion overlying the dust flaps and a tuck fiapportion depending therefrom along the inside surface of the body portionto provide a closure for the other end of said container.

9. The blank in accordance with claim 7 wherein each of said dust flapson the said one edge of the blank has a nose projecting from the freeend thereof at the sides adjacent the bottom end wall flap and thebottom end wall flap has a pair of spaced arcuate slits adjacent theinner end thereof into which said noses of the dust fiaps are adapted toextend upon folding of the blank.-

lltl. A container integrally formed of synthetic plastic sheeting havingfour hingedly connected wall panels defining a rectangular body and abody-locking fiap along the side margin of one of the outer of said wallpanels extending normally thereto and overlying the other of said outerwall panels, said overlain wall panel having a locking incision thereinadjacent the free end thereof and said body-locking fiap having alocking tab thereon engaged in said locking incision, one of said oneouter wall panel having the body-locking flap and the wall panelopposite thereto having a bottom end wall panel hingedly connected alongits bottom edge and extending normally thereto and the other of said oneouter wall panel and wall panel opposite thereto having an end-lockingflap hingedly connected along its bottom edge and extending normallythereto along the outer surface of said end wall panel, a pair of dustflaps hingedly connected along the bottom edge of the remaining wallpanels disposed therebetween and extending normally thereto, said endWall panel having a locking incision therein and said endlocking flapbeing disposed outwardly of said end wall panel and dust fiaps andhaving a locking tab thereon engaged in said locking incision of the endwall panel to hold said end wall panel and dust flaps in firm assemblyand providing a bottom wall closure for said container, and flapshingedly connected along the other edge of said body wall panelsproviding a top wall closure for said container, at least one of saidlocking incisions being comprised of a pair of spaced curvilinear slitsand a slit extending transversely thereof and intersecting saidcurvilinear slits intermediate their length to provide a pair of hingedflaps, the spacing between said curvilinear slits varying along thelength thereof, the cooperating locking tab being of generallydovetailed configuration with its free end being of greater width thanthe spacing between said curvilinear slits at their point of widestdivergence and with its sides tapering to a root portion of lesser widththan the spacing between the curvilinear slits at their point ofgreatest divergence, said one locking tab extending inwardly of thecooperating locking incision at a point spaced toward the free end ofthe underlying panel and having its free end portion disposed along theinner surface of the underlying panel outwardly of said incision, saidtab being disposed outwardly of the hinged flap adjacent the outer edgeof the underlying panel and the other of said hinged flaps beingdisposed outwardly of said tab, said hinged flaps between thecurvilinear slits resiliently bearing against both surfaces of said tab,

11. The container in accordance with claim 10 wherein said syntheticplastic sheet material is biaxially oriented polystyrene of 5 to 15 milsthickness.

12. The container in accordance with claim 10 wherein said lockingincisions are each comprised of a pair of opposed generally S-shapedslits and a slit extending transversely thereof and intersecting saidS-s-haped slits, said S-shaped slits having opposed arcuate portions atthe ends spaced away from the free end of the panel and reversely curvedportions with their terminal portions extending towards each other atthe ends adjacent the free end of the panel, said transverse slitintersecting said opposed arcuate portions at a point spaced towards thefree end of the panel from their point of closest proximity andproviding a pair of hinged flaps between said S-shaped slits and whereinsaid locking tabs are each of generally dovetailed configuration withits free end being of greater width than the spacing between saidS-shaped slits and tapering inwardly to a reduced width at its rootportion which is greater in width than the spacing between the opposedarcuate portions at their point of closest proximity but of lesser widththan the spacing between the reversely curved arcuate portions at theirpoint of greatest separation, said locking tabs extending inwardly ofthe incision at a point spaced towards the free end of the underlyingpanel from the point of closest proximity between said opposed arcuateportions with the sides of the free end portion of the locking tab beingdisposed along the inner surface of the underlying panel outwardly ofsaid incision at said opposed arcuate portions, said tabs being disposedoutwardly of the hinged fiap between the S-shaped slits adjacent theouter edge of the underlying panel and the other of said hinged flaps isdisposed outwardly of said tab, and said hinged flaps between the S-shaped slits resiliently bearing against the surfaces of said tabs.

13. A container integrally formed of synthetic plastic sheeting havingfour hingedly connected wall panels defining -a rectangular body and abody-locking flap along the side margin of one of the outer of said wallpanels extending normally thereto and overlying the other of said outerwall panels, said overlain wall panel having a locking incision thereinadjacent the free end thereof and said body-locking flap having alocking tab thereon engaged in said locking incision, an end lockingfiap hingedly connected along the bottom edge of said one outer wallpanel with the body-locking flap and extending normally thereto, an endwall panel hingedly connected along the bottom edge of the wall panelopposite to that having said end locking flap and extending generallyparallel thereto, a pair of dust flaps hingedly connected along thebottom edge of the remaining wall panels disposed therebetween andextending normally thereto, said end Wall panel having a lockingincision therein and said endlocking flap being disposed outwardly ofsaid end wall panel and dust flaps and having a locking tab thereonengaged in said locking incision of the end wall panel to hold said endwall panel and dust flaps in firm as sembly and provide a bottom wallclosure for said container, and a top end wall panel and top dust flapshingedly connected along the other edge of said body wall panelsproviding a topwall closure for said container, at least one of saidlocking incisions being comprised of a pair of spaced curvilinear slitsand a slit extending transversely thereof and intersecting saidcurvilinear slits intermediate their length to provide a pair of hingedflaps, the spacing between said curvilinear slits varying along thelength thereof, the cooperating locking tab being of generallydovetailed configuration with its free end being of greater width thanthe spacing between said curvilinear slits at their point of widestdivergence and with its sides tapering to a root portion of lesser widththan the spacing between the curvilinear slits at their point ofgreatest divergence, said one locking tab extending inwardly of thecooperating locking incision at a point spaced toward the free end ofthe underlying panel and having its free end portion disposed along theinner surface of the underlying panel outwardly of said incision, saidtab being disposed outwardly of the hinged flap adjacent the outer edgeof the underlying panel and the other of said hinged flaps beingdisposed outwardly of said tab, said hinged flaps between thecurvilinear slits resiliently bearing against both surfaces of said tab.

14. A container integrally formed of synthetic plastic sheeting havingfour hingedly connected wall panels defining a rectangular body and abody-locking flap along the side margin of one of the outer of said wallpanels extending normally thereto and overlying the other of said outerwall panels, said overlain wall panel having a pair of locking incisionstherein adjacent the free end thereof and spaced apart along said freeend and said body-locking flap having a pair of locking tabs spacedalong the free end thereof and engaged in said locking incisions, anend-locking flap hingedly connected along the bottom edge of the wallpanel having the bodylocking flap and extending normally thereto, an endwall panel hingedly connected along the bottom edge of the wall panelopposite to that having said end-locking flap and extending generallyparallel thereto, dust flaps hingedly connected along the bottom edge ofthe remaining body wall panels disposed therebetween and extendingnormally thereto along the surface of said end wall panel, said end wallpanel having a locking incision therein, and said end-locking flapextending outwardly of said dust flaps and end wall panel and having alocking tab thereon engaged in said locking incision of the end wallpanel to hold said end wall panel and dust flaps in firm assembly andproviding a bottom wall closure for said container, and a top end wallpanel and top dust flaps hingedly connected along the other edge of saidwall panels normally thereto and providing a top wall closure for saidcontainer, said locking incisions each being comprised of a pair ofopposed generally S-shaped slits and a slit extending transverselythereof and intersecting said S-shaped slits, said S-shaped slits havingopposed arcuate portions at the ends spaced away from the free end ofthe panel and reversely curved portions with their terminal portionsextending towards each other at the ends adjacent the free end of thepanel, said transverse slit intersecting said opposcd arcuate portionsat a point spaced towards the free end of the panel from their point ofclosest proximity and providing a pair of hinged flaps between saidS-shaped slits, said locking tabs each being of generally dovetailedconfiguration with its free end being of greater width than the spacingbetween said S-shaped slits and tapering inwardly to a reduced width atits root portion which is greater in width than the spacing between theopposed arcuate portions at their point of closest proximity but oflesser width than the spacing between the reversely curved arcuateportions at their point of greatest separation, said locking tabsextending inwardly of said incision at a point spaced towards the freeend of the underlying panel from the point of closest proximity betweensaid opposed arcuate portions with the sides of the free end portion ofthe locking tab being disposed along the inner surface of the underlyingpanel outwardly of said incision at said opposed arcuate portions, saidtabs being disposed outwardly of the hinged flap between the S-shapedslits adjacent the outer edge of the underlying panel and the other ofsaid hinged flaps is disposed outwardly of said tab, and said hingedflaps between the S-sh-aped slits resiliently bearing against thesurfaces of said tabs.

15. The container in accordance with claim 14 wherein said top end wallpanel is hingedly connected to the other edge of the body wall panelhaving the locking incisions and extending normally thereto and said topdust flaps are hingedly connected to the other edge of the body wallpanels having said end locking flap and bottom end wall panel andextending normally to said body Wall panels, said top end wall panelhaving a top wall portion overlying said top dust flaps and having atuck portion at its free end extending normally to said top wall portionalong the inner surface of the container and resiliently lfaearingthereagainst to provide a top wall closure there- 16. The container inaccordance with claim 14 wherein said bottom dust flaps are disposedoutwardly of the bottom end wall flap and have a nose projecting fromthe free end thereof at their opposed side edge sand wherein said bottomend wall flap has a pair of spaced arcuate slits adjacent the inner endthereof through which the noses of said dust flaps extend.

17. A container formed from semi-rigid synthetic plastic sheet materialand having a first panel extending in one direction in overlyingrelationship to a second panel extending in the opposite direction, saidsecond panel having a locking incision therein spaced inwardly from thefree end thereof and comprised of a pair of opposed generally S-shapedslits and a slit extending transversely thereof and intersecting saidA-shaped slits, said S-shaped slits having opposed arcuate portions atthe ends spaced away from the edge of the blank and reversely curvedportions with their termini extending towards each other at the endsadjacent the edge of the blank, said transverse slit intersecting saidopposed arcuate portions at a point spaced towards the edge of the blankfrom their pomt of closest proximity and providing a pair of hingedflaps between said S-shaped slits, said first panel having a locking tabprojecting from the free end thereof and engaged in said lockingincision of the second panel, said locking tab being of generallydovetailed configuration with its free end being of greater width thanthe spacing between said S-shaped slits and tapering inwardly to areduced width at the root portion which is of greater width than thespacing between the opposed arcuate portions at their point of closestproximity but of lesser width than the spacing between the reverselycurved arcuate portions at their point of greatest separation, saidlocking tab extending inwardly of said locking incision at a pointspaced towards the free end of said second panel from the point ofclosest proximity between said opposed arcuate portions with the sidesof its free end portions being disposed along the inner surface of saidsecond panel outwardly of said locking incision at said opposed arcuateportions, said locking tab overlying the hinged flap between theS-shaped slits adjacent the free end of said second panel and the otherof said hinged flaps overlying said locking tab, said hinged flapsresiliently bearing again-st the surfaces of said locking tab to providefirm engagement.

18. The container in accordance with claim 17 wherein said first panelhas a pair of locking tabs spaced along the free end thereof and whereinsaid second panel has a pair of locking incisions spaced inwardly andalong the free end thereof.

19. A blank of semi-rigid synthetic plastic material for folding into acontainer with one portion thereof bemg adapted to extend in onedirection along the outer surface of a second portion extendingoppositely thereof, said portion having a locking incision thereinspaced inwardly from the outer edge thereof and comprised of a pair ofopposed generally S-shaped slits and a slit extending transverselythereof and intersecting said S-shaped slits, said S-shaped slits havingopposed arcuate portions at the ends thereof spaced away from the outeredge of the blank and reversely curved portions with their terminiextending towards each other at the ends adjacent the outer edge of saidblank, said transverse slit intersecting said opposed arcuate portionsat a point spaced towards the outer edge of the blank from their pointof closest proximity and providing a pair of hinged fiaps between saidS-sh-aped slits, one portion of the blank having a locking tabprojecting from the outer edge thereof and of generally dovetailedconfiguration with its free end being of greater width than the spacingbetween said S- shaped slits, said tab tapering inwardly to a reducedwidth at the root portion which is of greater width than the spacingbetween the opposed acruate portions at their point of closest proximitybut of lesser width than the spacing between the reversely curvedarcuate portions at their point of greatest separation, said tab beingadapted to extend inwardly of said locking incision at a point spacedtowards the edge of the underlying second portion from the point ofclosest proximity between said opposed arcuate portions with the sidesof its free end portions being disposed along the inner surface of theunderlying second portion outwardly of said incision at said opposedarcuate portions whereby said tabs will overlie the hinged flapsadjacent the edges of the underlying second portion and the others ofsaid hinged flaps will overlie said tab and said hinged flaps willresiliently 14 bear against the surfaces of said tab to provide firmengagement.

20. The blank in accordance with claim 19 wherein said one portion has apair of locking tabs spaced along the free end thereof and wherein saidsecond portion has a pair of locking incisions therein spaced inwardlyfrom and along the free end thereof.

21. A container integrally formed of semi-rigid syn thetic plastic sheetmaterial having four hingedly connected wall panels defining arectangular body and a flap hingedly connected to one of said wallpanels and overlying another of said wall panels, said overlain wallpanel having a locking incision in the overlain portion thero'f and saidflap having a locking tab thereon engaged in said locking incision, saidlocking incision being comprised -of a pair of opposed generallyS-shaped slits and a slit extending transversely thereof andintersecting said S-shaped slits, said S-shaped slits having opposedarcuate portions at the ends spaced away from the inner edge of theoverlain portion and reversely curved portions with their terminiextending towards each other at the other ends, said transverse slitintersecting said opposed arcuate portions at a point spaced towards theinner edge of the overlain portion from their point of closest proximityand providing a pair of hinged flaps between said S-shaped slits, saidlocking tab being of generally dovetailed configuration with its freeend being of greater width than the spacing between said S-shaped slitsand tapering inwardly to a reduced width at its root portion which isgreater in width than the spacing between the reversely curved arcuateportions at their point of greatest separation, said tab being adaptedto extend inwardly of said incision at a point spaced towards the inneredge of the overlain portion from the point of closest proximity betweensaid opposed arcuate portions with the sides of its free end portionbeing disposed along the inner surface at the overlain panel outwardlyof said incision at said opposed arcuate portions whereby said tab willoverlie the hinged flap adjacent the inner edge of the overlain paneland said hinged flaps will resiliently bear against the surfaces of saidtab to provide firm engagernent.

References Cited by the Examiner UNITED STATES PATENTS 2,190,433 2/1940Palmer 22937 2,209,593 7/ 1940 Bernis 22939 2,658,660 11/1953 Keller229-39 3,019,957 2/1962 Palmer 22935 JOSEPH R. LECLAIR, PrimaryExaminer.

R. PESHOCK, Examiner.

1. AN UNSCORED CONTAINER BLANK INTEGRALLY FORMED OF SEMI-RIGID SYNTHETICPLASTIC SHEET MATERIAL AND INCLUDING A BODY PORTION ADAPTED TO BECOLD-FOLDED INTO FOUR WALL PANELS DEFINING A CONTAINER BODY OFRECTANGULAR CONFIGURATION AND A SIDE-LOCKING FLAP ALONG ONE OUTER SIDETHEREOF, SAID BLANK HAVING A LOCKING TAB ON SAID ONE OUTER SIDE AND ACOOPERATING LOCKING INCISION ADJACENT THE OTHER OUTER SIDE THEREOF FORINTERENGAGEMENT UPON FOLDING OF THE BLANK INTO THE RECTANGULAR BODYCONFIGURATION, SAID BLANK BEING INCISED ALONG ONE EDGE AT THE LINES OFINTENDED FOLD FOR THE WALL PANELS OF THE BODY TO PROVIDE A BOTTOM ENDWALL FLAP, A PAIR OF DUST FLAPS AND AN ENDLOCKING FLAP AND ADAPTED TOPROVIDE A CLOSURE FOR ONE END OF THE CONTAINER, SAID END-LOCKING FLAPAND END-WALL FLAP BEING SPACED APART BY A DUST FLAP AND ONE OF SAIDLOCKING FLAP AND END-WALL FLAP EXTENDING FROM THE PORTION OF THE BLANKADJACENT SAID LOCKING FLAP OF THE BODY PORTION, ONE OF SAID LOCKING FLAPAND END WALL FLAP HAVING A LOCKING INCISION THEREIN AND THE OTHER OFSAID LOCKING FLAP AND END WALL FLAP HAVING A LOCKING TAB THEREONENGAGEABLE IN SAID INCISION TO PROVIDE A FIRM CLOSURE, SAID BLANK BEINGINCISIED ALONG THE OTHER EDGE THEREOF AT THE LINES OF INTENDED FOLD FORTHE SAID WALL PANELS TO PROVIDE FLAPS ADAPTED TO BE FOLDED INTO ACLOSURE FOR THE OTHER END OF SAID BODY, AT LEAST ONE OF SAID LOCKINGINCISION BEING COMPRISED OF A PAIR OF SPACED CURVILINEAR SLITS AND ASLIT EXTENDING TRANSVERSELY THEREOF AND INTERSECTING SAID CURVILINEARSLITS INTERMEDIATE THEIR LENGTH TO PROVIDE A PAIR OF HINGED FLAPS, THESPACING BETWEEN SAID CURVILINEAR SLITS VARYING ALONG THE LENGTH THEREOF,THE COOPERATING LOCKING TAB BEING OF GENERALLY DOVETAILED CONFIGURATIONWITH ITS FREE END BEING OF GREATER WIDTH THAN THE SPACING BETWEEN SAIDCURVILINEAR SLITS AT THEIR POINT OF WIDEST DIVERGENCE AND WITH ITS SIDESTAPERING TO A ROOT PORTION OF LESSER WIDTH THAN THE SPACING BETWEEN THECURVILINEAR SLITS AT THEIR POINT OF GREATEST DIVERGENCE, SAID ONE TABBEING ADAPTED TO EXTEND INWARDLY OF SAID ONE LOCKING INCISION WHEREBYSAID TAB WILL OVERLIE THE HINGED FLAP ADJACENT THE EDGE OF THEUNDERLYING PANEL AND THE OTHER OF THE HINGED FLAPS DEFINED BY SAIDINCISION WILL OVERLIE SAID TAB AND SAID HINGED FLAPS WILL RESILIENTLYBEAR AGAINST THE SURFACES OF SAID ONE TAB TO PROVIDE FIRM ENGAGEMENT.